Questions. 1) What did the early alchemists spend most of their time on?

1) What did the early alchemists spend most of their time on?

2) Is radium one of the radioactive elements?

3) What is a common use of radium?

4) What can carelessly used radium cause?

5) Whom was radium discovered by?

Note

1)alchemists - алхимики

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^SALT

“He is the salt of the earth.”¹ “He is not worth his salt.”² Both of these are common sayings. They show that salt is an important substance. It is even more important today than in the past.

At times salt has been used as money. The word salary comes from sal, the Latin word for "salt". The Roman soldiers used to be paid partly in salt.

The Arabs used to believe that eating another person's salt meant that you would do him no harm. It was a bad sign if anyone refused to eat salt when he was a guest. In some parts of Africa it is still good manners, when you meet a friend, to let him lick your cake of salt.

There are superstitions about salt, too. Spilling salt is supposed to bring bad luck. But the person who spills the salt can keep the bad luck away if he throws a little over his left shoulder. Another supersti­tion is that you can catch a bird if you sprinkle a little salt on its tail.

Salt is something which everyone has to have. We cannot live without it. Of course, most of us like the taste of salt, too.

Sea water has salt in it. But most of the salt we buy comes from deep in the ground. It comes from layers of rock salt there. The layers were formedwhen salty seas of long ago evaporated. Later, the salt was covered with other rocks.

It is not hard to get salt from the layers of rock salt underground. Mines can be dug down, and the salt taken out in blocks. Or water can be forced down through pipes to the salt and then pumped up again. The salt that has been dissolved in the water can easily be taken out of it.

Most of the salt we buy is in tiny crystals. Under a microscope they look like tiny cubes of glass.

Chemicals made from salt are used in the manufacture of rubber, and steel, and dyes, and dyes. Chemicals from salt are used to soften water and to bleach cloth. They help in scouring wool and making leather. The list could go on andon. A great many of our factories of today would be forced to shut down if there were no more salt.

Дата добавления: 2015-07-20